Steam Possible Bug: Class 66 Will Not Start With Reverser In, Scenario "hoo Dares Inn"

I am in TSW 3 (sic) doing the scenario "Hoo Dares Inn" with the Class 66 locomotive. I can shut it down, set the isolation switch to "start stop isolate", press the green start switch and it refuses to start. However, if I take out the reverser and press the green switch again, it will start. AFAICT it should start with the reverser in and moreover require it is in, not out. Is this a bug?